Exercise equipment has been designed to facilitate a variety of exercise motions. For example, treadmills allow a person to walk or run in place; stepper machines allow a person to climb in place; bicycle machines allow a person to pedal in place; and other machines allow a person to skate and/or stride in place.
Yet another type of exercise equipment has been designed to facilitate relatively more complicated exercise motions and/or to better simulate real life activity. Some examples of elliptical motion machines are disclosed in published German Patent Appl'n No. 29 19 494 of Kummerlin; U.S. Pat. No. 4,185,622 to Swenson; U.S. Pat. No. 5,242,343 to Miller; U.S. Pat. No. 5,423,729 to Eschenbach; and U.S. Pat. No. 5,529,555 to Rodgers, Jr.
On one hand, an advantage of elliptical motion exercise machines is that a person's feet travel both up and down and back and forth during an exercise cycle. On the other hand, a disadvantage of these machines is that the person's feet are constrained to travel through a path which is substantially limited in terms of size and/or configuration from one exercise cycle to the next. Although the above-identified references disclose how to adjust the path of foot travel, the methods are relatively crude, and room for improvement remains.